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Question 19M.3.SL.TZ2.9b

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Date May 2019 Marks available [Maximum mark: 3] Reference code 19M.3.SL.TZ2.9b
Level SL Paper 3 Time zone TZ2
Command term Calculate Question number b Adapted from N/A
b.
[Maximum mark: 3]
19M.3.SL.TZ2.9b

The moment of inertia of a solid sphere is  I = 2 5 m r 2 where m is the mass of the sphere and r is the radius.

(b)

A solid sphere of mass 1.5 kg is rolling, without slipping, on a horizontal surface with a speed of 0.50 m s-1. The sphere then rolls, without slipping, down a ramp to reach a horizontal surface that is 45 cm lower.

Calculate the speed of the sphere at the bottom of the ramp.

[3]

Markscheme

Initial  E K = 7 10 × 1.50 × 0.5 2 «=0.26J»  ✔

Final  E K = 0.26 + 1.5 × 9.81 × 0.45  «=6.88J»  ✔

v = « 10 7 × 6.88 1.5 = » 2.56 «m s–1»  ✔

 

Other solution methods are possible.

 

Examiners report

Although there were many correct answers, many candidates forgot to include the initial kinetic energy of the ball at the top of the ramp. The process followed to obtain the answer was too often poorly presented, candidates are encouraged to explain what is being calculated rather than just writing numbers.

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